Centrifuge rotors are typically used in laboratory centrifuges to hold samples during centrifugation. While centrifuge rotors may vary significantly in construction and in size, one common rotor structure is the fixed angle rotor having a solid rotor body with a plurality of cell hole cavities distributed circumferentially within the rotor body and arranged symmetrically about an axis of rotation. Samples are placed in the cavities, allowing a plurality of samples to be subjected to centrifugation.
Conventional fixed angle centrifuge rotors may be made from metal or various other materials. However, a known improvement is to construct a centrifuge rotor by a compression molding and filament winding process wherein the rotor is fabricated from a suitable material such as composite carbon fiber. For example, a fixed angle centrifuge rotor may be compression molded from layers of resin-coated carbon fiber laminate material. Examples of fixed angle composite centrifuge rotors are described in U.S. Pat. Nos. 5,833,908, 6,056,910, 6,296,798, 8,147,392, and 8,273,202, each disclosure of which is expressly incorporated herein by reference in its entirety.
Because centrifuge rotors are commonly used in applications where the rotational speed of the centrifuges may exceed hundreds or even thousands of rotations per minute, it is important that centrifuge rotors are formed with structure designed to withstand the stresses and strains experienced during the high speed rotation of the loaded rotor. An improvement for providing structural rigidity to the rotor body during centrifugation is described in U.S. Pat. No. 8,323,169 (also owned by the common assignee), the disclosure of which is expressly incorporated herein by reference in its entirety. In that improvement, a pressure plate is coupled to a bottom portion of the rotor body, such that the pressure plate supports the tubular cavities during rotation, thereby minimizing the likelihood of rotor failure.
While a primary source of stresses and strains experienced by a rotor during centrifugation includes outwardly directed centrifugal forces exerted by loaded cavities, an additional source is torque exerted by the rotating centrifuge spindle. More specifically, a central portion of the rotor where a rotor hub couples to the centrifuge spindle generates high degrees of torque during rotation of the rotor, particularly during rotational acceleration and deceleration. This torque results in high degrees of concentrated stress on various components of the rotor. Whereas performance capabilities of conventional rotors may be limited by their ability to accommodate such torque and resulting stress in addition to that caused by centrifugal forces, a need exists for centrifuge rotors having improved structural rigidity for mitigating the stresses and strains caused by various sources, including torque, during centrifugation.